Glyphosate and Saflufenacil: Elucidating Their Combined Action on the Control of Glyphosate-Resistant Conyza bonariensis

Cristiano Piasecki,Ivan R Carvalho,Luis A Avila,Leandro Vargas,Dirceu Agostinetto

doi:10.3390/agriculture10060236

Cristiano Piasecki, Ivan R Carvalho + Show 3 more

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https://doi.org/10.3390/agriculture10060236

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Abstract

Synergic effects of glyphosate and saflufenacil have been reported to control Conyza spp. However, the mechanism of this synergic combination is unknown. The objectives of this study were to investigate the effects of the combination of glyphosate and saflufenacil on the control and resistance status of glyphosate-resistant (GR) C. bonariensis, as well as on oxidative stress and lipidic peroxidation. Glyphosate-resistant and glyphosate-sensitive (GS) biotypes were treated with different rates of saflufenacil, glyphosate, and glyphosate combined with saflufenacil. The combination of glyphosate (1480 g ae ha−1) and saflufenacil (≥15 g ha−1) presented the best control of GR plants compared with their individual effects. It also reduced the resistance factor from 19.6 to 4.6 (4.3-fold) and represents a good alternative for resistance management. The combination of glyphosate and saflufenacil resulted in higher oxidative stress and lipidic peroxidation compared with the effects of either herbicide alone. The oxidative stress and lipid peroxidation promoted by the combination of the herbicides occurred earlier after treatment and remained at higher levels over a longer period (12–192 h) compared with their individual results. The combined oxidative stress and lipid peroxidation at high levels over a long time is likely to be one reason that the combination of glyphosate and saflufenacil effectively controls GR C. bonariensis.

Highlights

Weeds are historically one of the main factors that negatively affect crop yield worldwide [1].The interference of weeds with crops reduces the yield quantity and quality and, food availability, which causes an unparalleled economic impact downstream in the productive agricultural chain
reactive oxygen species (ROS) overproduction in different cellular organelles likely exceeds the antioxidant capacity to scavenge these toxic molecules, which results in severe cellular damage. Another observation is that the results indicate faster ROS production and cellular damage after saflufenacil application compared with glyphosate application, which took at least double the time of saflufenacil to cause similar effects
The present study hypothesized that the combination of glyphosate and saflufenacil would increase the control of GR C. bonariensis by causing high ROS production and oxidative stress

Summary

Introduction

Weeds are historically one of the main factors that negatively affect crop yield worldwide [1]. The interference of weeds with crops reduces the yield quantity and quality and, food availability, which causes an unparalleled economic impact downstream in the productive agricultural chain. It is estimated that non-controlled weeds reduce about 50% of major crop yields (soybean, rice, corn, etc.) [2]. The repetitive application of herbicides—in general, with the same mechanism of action—has led to the selection of naturally resistant variants of several weed species [4,5]. The evolution of weeds to acquire herbicide resistance has hindered weed control, increased crop yield losses, and increased the Agriculture 2020, 10, 236; doi:10.3390/agriculture10060236 www.mdpi.com/journal/agriculture

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